ASA 20" f/3.8 20N Newtonian Astrograph OTA w/ Accessories- Discontinued

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ASA 20" f/3.8 20N Newtonian Astrograph OTA w/ Accessories- Discontinued   Discontinued
Item # A2-ASA20NO3
  • This 500mm ASA 20N Newtonian Astrograph features a 20" f/3.8 flat-field low-expansion parabolic Suprax, < 1/7 Lambda wave P/V, 97% Reflection mirror, and includes a Zygo interferogram.
  • Includes a super-thin, sturdy double vane spider for reduced diffraction spikes.
  • Carbon fiber body is super strong and light, and is lined with black velvet to absorb stray light.
  • Accepts the ASA 3" focuser and an assortment of correctors for flexibility of focal length.
  • Includes laser collimator, focuser, flight ready case, and tube rings.


ASA 20" 20N Newtonian Astrograph OTA Only

All ASA astrographs have the highest quality, low-expansion Suprax primary and secondary mirrors (P/V <1>97% reflectivity), and come with their own interferogram. What's more, the primary mirror on the ASA 20N Astrograph includes a centered triangle reference mark for ease of collimation. All ASA astrograph telescope tubes are manufactured of sandwiched carbon fiber. The use of carbon fiber not only adds to the astrograph's visual appeal, but makes them up to 60% lighter while retaining rigidity. Due to the thermal stability of carbon fiber, focus remains stable over a long period of time, even when your environment fluctuates. The tube assembly's ability to remain stable also positively affects collimation.

All of the Newtonian astrograph telescopes by ASA have the same natural focal ratio (f/3.8) by design. You can achieve good signal-to-noise ratio with your CCD using short exposure times. Their system f/# can be reduced or increased easily by the user, meaning the natural focal length of the device can be shortened by a factor of 0.75x or increased by a factor of 1.8x, while retaining the highest-quality of imagery. You can enjoy all three telescope focal lengths, simply by using each of the three appropriate corrector lenses, which are sold separately.

But even more features await in this high quality ASA Astrograph Telescope. Their uncompromising optical design by Philipp Keller, Dipl. Physics, (Germany), and the use of the finest materials available, yields imaging performance covering a large field of view, a fast f/#, ultra-stable construction, yet they're light in weight. Testing has shown the finest spot sizes available in currently-available fast telescopes. Standard on the ASA 20" Newtonian Astrograph is the new "double thin spider." It is very rigid and its double-vane design significantly reduces annoying diffraction spikes from bright stars.

Please Note: The photos show an 8" 8N Astrograph and some optional equipment for illustration purposes. This 20" 20N Astrograph will be considerably larger, and does not include a focuser or any accessories so you can build out your ASA telescope the way you want it! This ASA Newtonian Astrograph is a special order item and requires a 20% deposit when you place your order, and the balance will be required before the telescope leaves Austria. This deposit is fully refundable as long as you cancel your order before the telescope is imported. Please email OPT or give one of our Telescope experts a call at 1-800-483-6287.

Additional Information

Additional Information

Manufacturer ASA
Telescope Series ASA Carbon Fiber
Optical Design Astrograph
Mount Type None - Optical Tube Only
Warranty 2 Year Warranty
Telescope Aperture 20"
Telescope Focal Length 1900mm
Telescope Focal Ratio f/3.8
Tube Color or Finish Carbon Fiber
Optical Tube Outer Diameter 590mm
Length of Optical Tube 1631mm
Optical Tube Weight 108.03lbs
Limiting Stellar Magnitude 16
Dew Shield Included? No, Not Necessary
Dew Shield Outside Diameter N/A
Finder Included None
Focuser Size 3"
Focuser Style Crayford
Manual or Electronic Focusing? Manual
Included Items

Included Items

  • ASA 20" 20N f/3.8 Newtonian Astrograph OTA
  • Tube Rings
  • 3" Focuser w/ 2" Adapter
  • OK Control Software
  • Controller & Cable
  • Fan Cable
  • Flightcase
  • Laser Collimator
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